Control Core switching out of ship upon load?

[Jeb42]

This is a new one to me.. for the past day I've been trying to get a small (standard hitchhiker container) living module up to my space station- no dice though. Once I get into orbit, and whenever I load the ship for the first time since starting the game it appears that whatever control module I'm using decides it doesn't like the company of whatever's placed below it and leaves. Just slides out with whatever I've attached (namely docking ports). When I quit to the space centre and load the ship up again however, it's fine. Honestly this isn't massive for me and it still works as part of the space station, but I'd really rather not have 4 Kerbals fly off every time I load the station up once again; it's really annoying. The only mod I'm using on this craft is AIES for a couple of small mono prop tanks in the hold and some ladders around the module. Here's a picture/video of my setup-

 

http://imgur.com/zsLg96S

whatever core I use, stock or not has the same problem

here's the video

 

edit: after placing a smaller core so it's not attached to the hitchhiker module, the game doesn't even bother sliding the parts out. it all just explodes (...)

 

thanks